68 patients had none to slight CT changes and 10 patients had moderate to severe changes noted on CT scans

V20 (volume of lung receiving at least 20 Gy) and older age were predictive of CT changes

V20 was the only predictor of vital capacity change. However, the maximum vital capacity change was 600 cc, with the vast majority less than 400 cc if at all

V20 and pre-radiation chemotherapy were predictive of DLCO changes. Again, these DLCO changes, for the most part, were mild.

96 patients had no symptoms of radiation pneumonitis and 29 patients had mild to moderate radiation pneumonitis changes

V20 and age were predictive of the development of symptoms of radiation pneumonitis

Author's Conclusions

V20 is the best predictor of radiological, physiological, and clinical symptoms of radiation pneumonitis. There was no use for V30.

Older age was an independent predictor of CT changes and the development of radiation pneumonitis

Pre-radiation chemotherapy also influences DLCO changes, perhaps due to chemotherapy's effect on membrane diffusion of alveoli.

This supports the further use of 3-D treatment planning on minimizing the dose to the lung.

Clinical/Scientific Implications

As noted above, lung toxicity from adjuvant radiation for breast cancer is a major concern. This study indicated that the most influential predictor on the development of lung toxicity is the amount of lung exposed to at least 20 Gy. This does lend support to the fact that 3-D planning should be used to decrease the amount of lung exposure as much as possible. However, the changes in CT scan have not been proven to be clinically useful and the physiological changes seen were small. In addition, the vast majority of patients developed no clinical symptoms or mild symptoms that presumably dissipated with conservative management. The largest causes of long-term toxicity in relation to the lung receiving radiation is the development of secondary malignancies (lung cancer) and progressive pulmonary toxicity. Although from this data, the development of irreversible lung disease from radiation theapy would be small, it is certainly not zero. Therefore, their baseline conclusion that 3-D planning should be used to spare the lung as much as possible is a logical one supported by their data.